First off, I'm not an expert tuner or pro wrench head, so if you ask questions, please know what your dealing with, I'll do my best. Hopefully rb240 (who is a tuner and a pro wrench head), who was also there and dyno'd his bike can properly address them. I'm sharing this to increase my knowledge and insight and maybe give others some information that would be useful.
rb240 and I did a dyno session with Nel's from 2 Wheel Dyno and Dave from Endrigo Racing this weekend...and from the results, it sure seemed worth it to us...but a lot of the things I thought were conventional wisdom got turned upside down...this is where I'm hoping I can learn from any discussions here as the resulting adjustments were not what I was expecting.
The results above are AFTER we got the bike running well enough to have a baseline, so the gains shown are already on top of the gains I got from the new head work, swapping off the exhaust and dropping down several jet sizes.
Final run results:
Max HP 9.8
Max Torque: 7.7
Max HP 8.38 (Revised: sorry had it at 9.4)
Max Torque: 6.74
I have some take-a-ways and I'm really interested in your thoughts on them:
- It seems that mufflers do make a difference, at least with the gys. My yosh + ghetto header was holding me back by a huge margin. The bike before dyno session topped at 60+ (gps verified) but on the dyno it barely broke 50 before the a/f mix went crazy. It was throwing out so much fuel out the pipe the dyno was reading it rich off the chart. If you are interested in that, I think I have a video of it and will post it up. We fixed it by putting on Tony's old pipe (pretty much a straight pipe with some can welded-on) and jetting down from the 130 jet we had tried on. Results: a/f stabalized torque and hp went up. The results above are AFTER we switched to Tony's pipe.
- Bike's were both running way rich and we've been going the wrong way. Most everyone out there says if you switch to after market filter and pipe you need to go with way bigger jetting. Maybe for some but for us it was the wrong way to go. I was running a 110 which is way smaller than the 120/130+ everyone told me I should be running. I'm down to a 108 and I'm STILL RICH, but I picked up a good horse just from jetting down. Tony's now running a 104 and he's still rich....we couldn't go lower because that was the smallest jet between us. We brought jets up to 145, expecting we'd have to move up..Note: We're up in Seattle, pretty much sea level and it was about 65 degrees and (as usual up here) raining...
- Ported head seemed to make a big difference. I have the Endrigo racing head on and my max HP is up to 9.8 and torque is way up. Nels and Dave figure thats the reason I'm putting up higher numbers than Tony's bike. I'm sad to say I didn't dyno my bike prior to the head work, but I had the slowest gy up in the NW and compared to other darkside bikes, it felt, well castrated.....porting gave it new life
- Cam looks like it makes a big difference. Check out rb240s video. His bike does a quick ramp up to 8K then proceeds to do this crazy 2nd stage ramp up to to 9K+ rpms. I'm not sure I have it on video, but he had another run after this one and the dyno read 10K rpms....It could be a number of things, but consensus was the A9 CAM was driving most of it...
- Carb needle position. I tended to not mess with it, but it makes a heck of a difference. Adjustments were made to both bikes, but rb240s was most pronounce. He was able to steady his HP FLAT across low, mid and high with a needle position change. You can actually see the base run and the final run graph on the video above. According to his graph (I'll try to get it posted up as it's not in my hands) he runs close to max HP all the way up the ladder. All he did between the runs was move the needle up....what the hell. As you can see I lose HP as I move up. Consensus was valve springs and CAM might change that...
There you have it, thanks for any insights,
- swapped pipe
- added Endrigo Racing Head
- dropped down several jet sizes
- changed the needle position on the carb
- adjusted a/f mix screw
- Posh CDI
- 8 pole stator
- Endrigo Racing Head
- Uni filter
- performance coil
- NGK spark plug end
- NGK plug
- exhaust is a combination of a header for a kymco 125 and half of a can for a 96 cr 250
- stock carb w/ aluminum intake manifold (ported to match head) running 108 mj/38 sj
- Dr. Pulley var w/ 13g sliders
- 842 gates belt
- 1500 rpm clutch spring
- 12" wheel w 120/70 tire (need to confirm tire size)